Help Center›FreeBASIC›Using the FreeBASIC compiler

Compiler Option: -entry

Documentation

Override the public exported name of the implicit user main function

Syntax



-entry < name >

Parameters

name

The custom name that overrides the public exported name of the implicit user main function

Description

The -entry compiler option changes the name of the publicly export symbol of the implicit user main function (automatically generated by fbc as start-up code).
It affects the start-up code and implicit user main, which is also affected by the module being the main module or not.

By default, fbc defines a publicly exported 'main' symbol in the main module as required by the run time start-up system code.
There is no other way currently to override fbc's use of the 'main' symbol other than to always compile and link separately.

Proceedings:

- The custom main function name must only be declared with the following signature (same parameter types, same return type, same calling convention) to be compatible with the (basic) main function:

'' internally the implicit main function is now named "custom_main"

Declare Function custom_main cdecl Alias "custom_main" ( ByVal argc As Long, ByVal argv As ZString Ptr Ptr ) As Long

- The (basic) main function must also be provided to satisfy the linker and start-up code. This might be defined in another libray or framework, in C, or ASM, or fb language as shown by the following minimum code example:

Function main cdecl Alias "main" ( ByVal argc As Long, ByVal argv As ZString Ptr Ptr ) As Long

    '' .....

    '' call the custom main

    Return custom_main( argc, argv )

End Function

- Then compile with the -entry custom_main option.

Note:

This feature is being developed and may change in future (see Compiler Option: -entry in Documentation forum).
There will maybe a better way to deal with this: a compiler option that lets to outright specify an explicit "main".

Example

Example of program (option_entry.bas) trying to show the minimal code for fb language only:

'' option_entry.bas:



'' - demonstrate alternate named main function

''   as an alternate entry point for the implicit user main

'' - we also can compile and link in separate steps



'' compile: $ fbc -c -m option_entry option_entry.bas -entry custom_main

'' compile: $ fbc option_entry.o

'' OR

'' compile: $ fbc option_entry.bas -entry custom_main





'' internally the implicit main function is now named "custom_main"

Declare Function custom_main cdecl Alias "custom_main" ( ByVal argc As Long, ByVal argv As ZString Ptr Ptr ) As Long



'' But we still need a main() function to satisfy the linker and start-up code

'' - this might be defined in another libray or framework

'' - it's not so let's define it here for the demonstration

Function main cdecl Alias "main" ( ByVal argc As Long, ByVal argv As ZString Ptr Ptr ) As Long

    '' just call our custom main for demonstration

    Return custom_main( argc, argv )

End Function





'' ---------------------------------

'' START OF USER'S IMPLICIT MAIN

'' internally this is named "custom_main" and will automatically be

'' called by our custom frame work



Print "hello"

Sleep



'' END OF USER'S IMPLICIT MAIN

'' ---------------------------------

Version

Since fbc 1.09.0